86 ELEMENTS OF STATIC ELECTRICITY. 



result : but, on replacing the coatings, a full discharge can 

 be obtained, the same as if they had not been removed. 



But if, while the coatings are removed, the jar be 

 examined by touching both surfaces with the finger and 

 thumb, or a small discharger, made with a bent wire, 

 at any point below a line marking the position of the 

 upper edges of the coatings, a discharge can be obtained 

 from that point. In this way a number of small dis- 

 charges can be had from various points, but no general 

 discharge. 



This proves that the charge remains on the glass, while 

 the coatings are removed ; but that the resistance of the 

 glass prevents a general discharge. But it cannot be 

 accepted as proof that the charge is confined to the 

 glass, when the coatings are in contact with it ; unless 

 it can be shown that the charge remains on the glass 

 after the removal of both coatings at precisely the same 

 instant ; which could not be done with the care neces- 

 sary for so delicate an experiment. But when the 

 coatings are removed separately, the charge must be 

 transferred to the glass during the removal of each : 

 since it is impossible to produce any change of poten- 

 tial on either surface, unless a corresponding change 

 is produced, at the same instant, on the opposite surface; 

 each being bound by the opposite. 



VARIOUS EFFECTS OF THE DISCHARGE. The dis- 

 charge of a Ley den jar of moderate size is sufficient to 

 explode gunpowder, and to ignite various substances; 

 as phosphorus, powdered resin, sulphuric ether, and 

 alcohol; while that of a large Leyden battery fuses 

 wires, magnetizes steel, 'and destroys animal life. 



With a battery of 550 square feet of coated surface, 

 large steel bars have been magnetized, iron wires, T o 



